1. Field of the Invention
The present invention relates to a process for preventing the agglomeration of powders through the use of triethylenediamine polymers as an agglomeration preventing agent for agglomerative powders.
Generally, powders often agglomerate on account of their coagulating and adhesive properties while they are kept in a silo or drum container. Hygroscopic or sublimative powders especially, are apt to agglomerate in the presence of a small amount of water or when the temperature is elevated. These agglomerative powders should be treated with care, otherwise difficulties in handling will result if the powders agglomerate. Countermeasures to prevent the agglomeration of said agglomerative powders to be used, include increasing the particle size of the powders, removing impurities in the powders, addition of an agglomeration preventing agent to the powders, storage of the powders in a tightly closed vessel, and covering the surface of the powder with an appropriate material (microcapsule). However, powders of amines such as piperazine triethylenediamine, anthraquinone and derivatives thereof and benzoic acid derivatives readily agglomerate with a slight elevation in temperature even when stored in a tightly closed vessel. On the other hand, strongly sublimative substances such as piperazine and triethylenediamine monomer more readily agglomerate when purified, which creates a serious problem for the prevention of agglomeration. These substances still retain their agglomerative property even when their particle size is increased. The agglomeration of the sublimative powders may be attributed to the fact that the particle substances are subjected to continuous sublimation and condensation, thereby increasing the contact area between the particles.
A conventional agglomeration preventing process which is effective for every particle including sublimative powders is to add an agglomeration preventing agent and also to form microcapsules.
Selection of the agglomeration preventing agent should be made with consideration of the following conditions. The addition can be minimized to achieve the purpose; the addition does not cause discoloration of the powders or does not give odor to the powders; physical properties of the powders are not affected or the effect, if any, can be minimized; and the agent does not cost much.
2. Description of the Prior Art
Conventionally agglomeration preventing agents used include powders of silica, inorganic salts such as Na.sub.2 S.sub.2 O.sub.5 and liquids such as polyethyleneglycol. They are required to be applied in a relatively large amount, 0.02-1% by weight, in order to have a significant effect. The microcapsule process requires, in addition to the preparation of the powders, additional processes such as spray drying, vacuum evaporation and interfacial polymerization to make microcapsules. This process needs many kinds of machines and apparatus and operations thereof are troublesome.
Further, when an inorganic salt such as Na.sub.2 S.sub.2 O.sub.5 or a liquid such as polyethyleneglycol is used, for instance, with triethylenediamine monomer, the physical properties of the monomer would probably be affected and therefore unable to be used for their particular purpose, such as catalyst for polyurethane.